1. Field of the Invention
The present invention generally relates to a semiconductor integrated circuit, and in particular to a window comparator circuit suitable for the semiconductor integrated circuit.
2. Description of the Related Art
A window comparator outputs a different voltage signal depending on whether an input voltage falls into a predetermined voltage range (hereinafter referred to as a window). In general, such a window comparator includes two operational amplifiers to produce a window. More specifically, a first operational amplifier compares the input voltage with a first reference voltage and a second operational amplifier compares the output of the first operational amplifier with a second reference voltage.
However, the conventional window comparator is not suitable for a semiconductor integrated circuit. In other words, it is hard to form the conventional circuit arrangement of a window comparator on a semiconductor substrate using a bipolar process.